How to Bake Polymer Clay

Before you turn anything on, slide an oven thermometer onto the middle rack. Cheap kitchen thermometers cost ten or fifteen dollars and they're the only honest way to know what temperature your oven is actually running.

Your dial says 130°C, but your oven might really be hitting 110 or 150. Polymer clay's working window is narrow - off by 20 degrees and you'll either burn pieces or leave them brittle. The thermometer takes the guesswork out.

Read the temperature on your specific clay packet - different brands run from about 110°C up to 140°C. Set the oven dial accordingly and let it preheat fully before putting any clay in.

Cold-oven baking is the fastest way to under-cure pieces. The clay sits at warming temperatures for the first few minutes instead of curing temperature, so the timer runs out before the clay actually cooks. Wait for the thermometer to confirm temperature before moving on.

Polymer clay needs an even surface that conducts heat smoothly. A glossy ceramic tile from any hardware store works best - the glaze keeps clay from sticking and the mass holds heat steady. Plain copy paper or baking paper on a tray are decent backups.

Space pieces so they aren't touching. Slide the tile onto the middle rack of the oven once it's preheated. Don't put pieces on a metal pan directly - hot spots scorch the bottoms.

Set a timer for 30 minutes minimum. Polymer clay needs that full window for the plasticizers to fully cure - cutting it short to 15 or 20 minutes is the most common reason pieces come out brittle.

Good news: at the right temperature, polymer clay can't really over-bake. 40 minutes, 50 minutes, even an hour is fine. So if you're doing thicker pieces or aren't sure, leave them in longer rather than shorter.

Pull pieces out and let them cool to room temperature - clay is fragile while it's still warm. Once cool, pick a thin piece and try to flex it gently between your fingers.

Properly cured polymer clay has a tiny bit of give. That flex means the plasticizers locked in correctly. If the piece snaps cleanly in half, or if drilling a jump-ring hole crumbles the clay around it, you under-baked. Pop the rest of the batch back in for another 15-20 minutes - you can always re-bake.